<!DOCTYPE html>
<html>
<body>

<div id="x" style="background: lightgreen; height: 3em; width: 400px; padding: 4px;">
  <div style="text-indent: 40%; width: 200px; background: yellow;">X</div>
</div>

<script>
var x = document.getElementById('x');
x.offsetWidth;
x.style.width = '500px';
</script>
</body>
</html>
